RU2127334C1 - Method of polishing copper and copper-base alloys - Google Patents

Abstract

FIELD: electrochemical treatment; may be used in process of electropolishing in various fields of engineering such as electrical engineering, instrumentation engineering for decorative purposes in manufacture of consumer goods from copper and its alloys. SUBSTANCE: at the first stage a part is treated for 3-10 min with voltage of 300-360 V and temperature of 60-90 C in solution containing ammonium phosphate in the amount of 3-5 wt.%; phosphoric acid up to attaining pH 5-7; water, the balance. At the second stage, treatment lasts for 10-30 s with voltage of 320-360 V and temperature of 70-90 C in aqueous solution containing, wt.%: ammonium phosphate, 3-5; potassium, sodium tartrate, 1-3; water, the balance. EFFECT: extended technological potentialities due to treatment of nonferrous metals and alloys; reduced aggression and toxicity of electrolytes.

Description

 The invention relates to electrochemical processing and can be used in electropolishing processes in various fields of technology: in the electrical industry, in instrument making and for decorative purposes in the production of consumer goods from copper and its alloys.

A known method of electrochemical polishing of copper [1], in which polishing is carried out on the anode in a potentiostatic mode at a voltage of 1.8 - 2.5 V, current density of 1.5 - 4.0 A / dm ² and a temperature of 17 - 30 ^o C in an electrolyte containing, wt.%:
Phosphoric Acid - 70 - 85
Metal aluminum - 0.05 - 2.0
A known method of polishing products from copper alloys [2], according to which the treatment is carried out for 0.5 min at a current density of 30 A / DM ² and a temperature of 25 ^o C in a solution of the composition, wt.%:
Phosphoric Acid - 81 - 87
Sulfuric acid - 5 - 7
Alkyl sulfate triethanolamine salt - 0.5 - 2.0
Water - Else
The disadvantage of the analogue is the high aggressiveness and toxicity of the electrolytes used, the complexity of the disposal and regeneration of spent solutions, as well as the difficult preliminary preparation of samples, including repeated degreasing, decapitation.

Closest to the technological essence of the claimed is a method of anodic polishing of products from copper and copper alloys using an electrolyte [3] containing phosphoric acid and copper ions, which consists in the fact that the products are sequentially passed through two baths filled with an electrolyte containing 75 - 90 wt.% phosphoric acid, 0.05 - 2.5 g of copper ions per 1 liter of phosphoric acid and additives of organic compounds. In this case, the first bath is maintained at a temperature of 70-100 ^° C and the process is carried out at an anode current density of 0.1-2 mA / cm ² , and in the second bath, the inlet temperature is maintained at 10-30 ^° C and at the outlet 60-140 ^° C (3). Operating voltage is regulated in the range of 1.5 - 2.5 V.

The disadvantage of the prototype is the high aggressiveness and toxicity of the electrolytes used, as well as their vapors at a processing temperature (up to 140 ^o C), as well as the complexity of the disposal and regeneration of spent solutions.

 The problem solved by the claimed invention is to reduce the aggressiveness and toxicity of electrolytes, as well as facilitating their regeneration.

The problem is solved in such a way that in the method of polishing copper and alloys based on it, including a two-stage electrolytic anode treatment, in contrast to the prototype, the sample is processed in the first stage for 3 to 10 minutes at a voltage of 300 - 360 V and a temperature of 60 - 90 ^o C in solution:
Ammonium Phosphate - 3 -6 wt.%
Phosphoric acid - up to pH 5 - 7
Water - Else
In the second stage - within 10 - 30 s at a voltage of 320 - 360 V and a temperature of 70 - 90 ^o C in an aqueous solution containing, wt.%:
Ammonium Phosphate - 3 - 5
Tartrate K, Na - 1 - 3
Water is the rest.

 At the first stage, the main removal of metal from the surface occurs, while the products of metal dissolution do not accumulate in the solution, since in this pH range the phosphates of copper, zinc, nickel and other metals included in copper alloys are poorly soluble and precipitate, which is significantly facilitates the regeneration of the solution.

 In the second stage, the oxide layer is removed with a leveled surface, which acquires a natural color and a mirror shine. A short treatment time in the second stage significantly increases the life of the electrolyte.

 An example of a specific implementation of the method.

 Example.

A copper sample is immersed in an electrolyte composition:
(NH ₄ ) ₃ PO ₄ - 5 wt.%
H ₃ PO ₄ - up to pH 5
Water - Else
heated to 80 ^o C. Processing is carried out at a voltage of 300 V for 4 minutes Then the sample is placed in an electrolyte composition, wt.%:
(NH ₄ ) ₃ PO ₄ - 5
Tartrate K, Na - 3
Water - Else
heated to 80 ^o C, treated at a voltage of 340 V for 15 s.

 After processing, the surface had a color inherent in copper and a specular gloss.

 Thus, the claimed invention allows electropolishing of copper and alloys based on it. This eliminates the use of toxic reagents and concentrated acids.

Sources of information
1. A.S. N 1768674, MKI 5 C 25 F 3/22, publ. BI N 38, 1992

 2. A.S. N 1788100. MKI 5 C 25 F 3/22, publ. BI N 2, 1993

 3. D.E. N 2322311, MKI 5 C 25 F 3/22, publ. 1975

Claims (1)

A method of polishing copper and alloys based on it, including a two-stage electrochemical anode treatment, characterized in that the treatment is carried out in the first stage for 3 to 10 minutes at a voltage of 300 - 360 V and a temperature of 60 - 90 ^o C in a solution of the composition:
Ammonium Phosphate - 3 - 5 wt.%
Phosphoric Acid - Up to pH 5 - 7
Water - Else
in the second stage for 10 - 30 s at a voltage of 320 - 360 V and a temperature of 70 - 90 ^o C in an aqueous solution containing, wt.%:
Ammonium Phosphate - 3 - 5
Tartrate K, Na - 1 - 3
Water - Else